There are two main types of near-eye displays: those which only provide a digital image to the eye, and those which combine a real-world view and with a secondary image such as a digital image, known as combiner or combining optics. Examples of digital only near-eye displays include displays used in night-vision monoculars and binoculars, and immersive displays (goggles, helmets) for gaming or simulation which completely block out the world view.